But how can 2.21 do that if
I made the kernel dump on 2.20? There's no dump folder for it to go off of to restore it. Not to mention, I'll likely lose all my save states. Surely, one would use the dump you made on 2.20 and restore on the same version, no?
This is my CYA (cover your ass) process:
Uninstall hakchi from the SNES Classic while you're on 2.20. You will get an alert at the end of that process that will ask you to reflash your stock kernel. Say Yes and it will do that for you. (Not strictly necessary--this is a "just in case" step, just in case a newer version of hakchi implements something that causes something flashed with the old version of hakchi to conflict with the OS, or something like that)
Close hakchi. Install 2.21 "in-place" (which means over the old version) instead of to a new location. The web installer is probably pretty nice for this. Your kernel dump will still be there. Your save states will still be there. Your games will still be there in the list. When computer programs are upgraded, the upgrade wizard usually does not delete all your documents, so you will be fine. You are installing it in-place, so everything will still be where 2.21 assumes they should be.
Make sure your settings are as you left them and make any changes you wish to make.
Reflash your custom kernel on 2.21.
Resynchronize your games.
Since you're nervous, be sure to make a copy of the hakchi version 2.20 folder before you upgrade it. All your sfroms, box art, config info, dumps, and stuff are in that folder. That way you can go back to 2.20 any time you want.
If anyone has any corrections, please let me know here.
Glad you're asking questions. Computer programs are knowable entities; when you learn how they work they stop sounding so scary. Hopefully this helps you!